<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
         *{
            margin:0;
            padding:0;
        }
        div{
            height:100px;
            width:100px;
            background-color: aqua;
            /* 垂直居中：文本、行内元素*/
            line-height: 100px;
        }
        span{
            display: inline-block;
            height:50px;
            width:100%;
            background-color: blue;
            /* 行内块(不能有文字)：垂直居中  line-height+ vertical-align: middle; */
            vertical-align: middle;
            /* line-height: 100px; */
        }
        img{
            height:20px;
            width: 20px;
            vertical-align: middle;
        }
    </style>
</head>
<body>
    <!-- <div>
        1111
    </div> -->
    <!-- <div>
        <span></span>
    </div> -->
    <div>
        <img src="1_09.png" alt="">
    </div>
    <!-- <div>
        <span>2222</span>
        <br>
        <i>3333</i>
        <br>
        <u>4444</u>
    </div> -->
</body>
</html>